Lubricating grease



Patented Nov. 20, 1951 LUBRICATING GREASE Arnold J. Morway, Clark Township, Union County, and David W. Young, Roselle, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application May 5, 1949, Serial No. 91,644

6 Claims.

The present invention relates to lubricating greases and particularly to a grease composition comprising an oil thickened with a combination thickener of high molecular weight soap and low molecular weight salt.

The preparation of lubricating greases, by thickening lubricating oils, usually of petroleum origin, with colloidal materials such as soaps, has long been a widespread practice. In recent years, it has been discovered that grease compositions of superior structure stability, es-

pecially at high temperatures, may be prepared by combining with the conventional soaps certain low molecular weight materials such as the water-soluble sulionates or the metal salts of the lower aliphatic acids such as acetic acid, acrylic acid, and the like. In our copending application, Serial No. 57,565, filed October 30, 1948, now Patent No. 2,516,136, there is also suggested the use of certain heterocyclic acid salts such as the sodium, lithium, .or calcium salts of furoic acid and its homologues.

The present invention is based upon the discovery that the metal salts of the low molecular weight cycloaliphatic and substituted alicyclic carboxylic acids may be used advantageously as the low molecular weight constituent of the soapsalt type greases mentioned above. The acid radical of such a salt should have a molecular weight of not more than about 160, hence alicyclic carboxylic acids having more than about 7 or 8 carbon atoms are not useful. Inasmuch as cyclopropanoic or .cyclopropane carboxylic acid, the lowest of the series, has the formula:

and its molecular weight is about 86, the molecular weight range of the acid radical may be said to vary from about 85 to 160.

In general, the present invention contemplates the use of a metal salt of an acid having the general formula (Rm)n()COOH where B may be hydrogen, halogen or a methyl group, is an alicyclic group of 3 to 6, preferably not more than carbon atoms. The letters in and n are small integers of 3 or less. Cyclopropanoic acid, or its cyclobutanoic or cyclopentanoic homologs are specifically preferred, but the chlorinated or methylated derivatives of these also may be used in some cases. I-Iexahydrobenzoic acid likewise may be used but it also approaches the maximum molecular weight.

The metallic radical in the salt should be an alkali or alkaline earth metal. Sodium, lithium, calcium, barium, and strontium are specifically preferred in that order. For convenience of manufacture, the metal radical preferably is the same as that of the soap. The soap may be a conventional soap of 012 to C24 acids or of the glycerides of the same fatty acid series.

For best results, the molar ratios of the low molecular weight salt and the higher molecular weight soap should be of the same order of magnitude. Thus, the best results are obtained by combining l to 2 mols of low molecular weight salt (based on the acid radical) with about 1 to 4 mols of the soap (also based on the acid radical). Since the soaps are usually formed from acids having a molecular weight of at least 200, the general Weight ratio of salt to soap, in the finished product is between about 1 to l and 1 to 6, preferably from 1 to 2 to about 1 to 4.

The grease compositions of the present invention consist, in general, of lubricating oil of 35 to 1000 S. U. S. viscosity at 100 F., thickened to a grease consistency with 1 to 10% by weight, based on the total composition, of the salt of the low molecular weight acid, combined with about 4 to 25% of the high molecular Weight soap, on the same basis. Thus, the oil preferably comprises from about to about of the total weight. The oil is preferably, though not necessarily in all cases, a mineral oil, or predominantly mineral base oil, with or without small quantities of conventional thickeners, anti-oxidants, corrosion inhibitors, tackiness agents, load carrying compounds, oiliness agents, and the like, as will be apparent to those skilled in the art.

The oil also may contain a small or large proportion of a synthetic lubricant, such as a dibasic acid ester (e. g., di-2-ethyl hexyl sebacate, adipate, or the like). Alternatively, polyglycol type synthetic oils may be used, or other synthetic oils such as the esters of dibasic acids and polyhydric alcohols. These may be mixed together in various proportions or they may be used in various proportions in petroleum base oil as desired, with limitations pointed out below.

Where it is desired to form the soap and the salt in situ, as is the preferred procedure at present, mineral oil only is preferably used as a carrier for the salt or soap-forming ingredients because otherwise the formation of soap or salt from alkaline materials may result in an incidental breakdown such as hydrolysis or partial hydrolysis of the synthetic ester lubricants. If desired, however, the quantity of mineral or petroleum oil so used may be merely sulfficient to suspend the salt and soap-producing acids and the saponifying metallic compounds while the reaction takes place to form the soap and the salt. Thereafter, the same type of oil, or any other compatible oil, synthetic or otherwise, may be added to obtain a grease of the required consistency.

It is specifically preferred to prepare the greases of this invention in the following general manner:

A mineral base lubricating oil, in quantity about one-third to one-half' of the amount of oil tobe used in the final grease is used as a vehicle and to this are added the fatty acids (or fatty oils if glycerides are used), the alicyclic acid from which the salt is to be formed, and

an aqueous solution of the saponifying agent,-

e. g., sodium hydroxide. The composition is heated, with contiued stirring, to a temperature somewhat above the boiling point of water, e. g., to about 250 F. It is held at such temperature until the Water in which the saponifying agent was dissolved and the water resulting from the saponification are substantially all evaporated. After saponificaticn and drying are thus completed, the remainder of oil (either mineral or synthetic as suggested above) is added and the temperature is further increased to a suitable grease cooking temperature while stirring is continued. The temperature eventually reached will depend upon the particular constituents, but it usually lies between about 350 and 600 F., preferably between 375 and 550 F. After cooking is complete, the grease is cooled appropriately and packaged. Cooling may be accomplished by conventional pan methods or, in the case of greases which crystallize properly, by the more rapid continuous cooling process. Anti-oxidants, such as phenyl alpha or phenyl beta naphthylamine may be added preferably after the temperature has dropped somewhat but may be introduced before, during or after cooling, as may other conventional additives.

The invention may be further explained by reference to the following specific examples, though obviously it is not limited thereby.

Example I A composition was prepared according to the general process described above, by neutralizing the acids and dispersing them in oil heated to 450 F. The grease was prepared from the following ingredients:

Cyclopropanoic acid per cent by weight 3.8 Hydrogeneated fish oil acids of C14 to C18,

predominantly (Hydrofol acids 54) per cent 15.0

NaOH (dry weight) do 4.0 Mineral lube oil, Coastal base, 55 S. U. S.

viscosity at 210 F. percent 772 The fatty acids used were substantially saturated. The molar ratio of the low molecular weight alicyclic acid to high molecular weight fatty acids was approximately 1 to 1. The resulting product, after cooling, was a smooth grease of good texture, having an excess alkalinity of 0.20% as NaOH. It was substantially insoluble in water up to temperatures of 150 F. This latter characteristic is not usual in soda base greases and indicates a further and important advantage of the present invention. This grease had a dropping point of 378 F., showing it to be suitable for use at fairly high temperatures. Its soap content was approximately 17% and its salt con- H2 Na OO-O-CHaCH:

HzC C O O CHQCH a PM 0 0H C O OGHaOH:

plus heat and 1110 I 7 Hz Example II A composition was prepared in the samegeneral manner as Example I, using the following ingredients:

Ingredients 6,2

Cyclopentane carboxylic Acid (Cyclopentanoic Acid) 6. 0 Hydrogenated Fish Oil Acids of C to C Predominantly (Hydrofol Acids 54) 1. 0

Characteristics Per Cent Free Alkalinity as NaOH 25 Dropping Point, F 384 Water Washing Test, 125 F.:

Water Temperature, Per Cent Loss 5.0 ASTM Penetration mm./l0-

60 Stroke 220 100,000 Strokes V 310 Wheel Bearing Test, 6 Hours at 220 F 1 Passes test satisfactorily.

The soap content of the finished grease of Example II was approximately 17% and the salt content was approximately 8% of the weight of the finishedproduct.

Examples I and 11 may be repeated by using essentially of 65 to by weight of mineral.

base lubricating oil, 1 to 10% of an alkali metal salt of a cycloalkanoic acid having 3 to 6 carbon atoms in the ring and having a molecular weight not greater than 160, and 4 to 25% of the same alkali metal soap of fatty acid hav-:

ing between 12 and 24 carbon atoms.

2. Composition as in claim 1 wherein the cycloalkanoic'acid is cyclobutanoic acid.

3. Composition according to claim 1 wherein said alkali metal is sodium.

4. Composition according to claim 1 wherein said alkali metal is lithium.

5. A lubricating grease consisting essentially" of a mineral base lubricating oil thickened to a grease consistency with about 17% by weight, based on the total composition 'of sodium soap 5 of predominantly C14 to C18 substantially saturated fatty acids and about 5% of the soda salt of cyclopropanoic acid.

6. A lubricating grease consisting essentially of a mineral base lubricating oil thickened to a grease consistency with about 17% of sodium soap of predominantly C14 to Cm substantially saturated fatty acids and about 8% of the soda salt of cyclopentanoic acid, said percentages being based upon the Weight of the total cOm- 19 6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,409,950 Meyer Oct. 22, 1946 2,468,098 Morway et a1. Apr. 26, 1949 2,468,099 Morway Apr. 26,. 1949 2,487,080 Swenson Nov. 8, 1949 2,516,137 Morway et a1 July 25, 1950 

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF 65 TO 95% BY WEIGHT OF MINERAL BASE LUBRICATING OIL, 1 TO 10% OF AN ALKALI METAL SALT OF A CYCLOALKANOIC ACID HAVING 3 TO 6 CARBON ATOMS IN THE RING AND HAVING A MOLECULAR WEIGHT NOT GREATER THAN 160, AND 4 TO 25% OF THE SAME ALKALI METAL SOAP OF FATTY ACID HAVING BETWEEN 12 AND 24 CARBON ATOMS. 